In 1988, Reuters reported on a radio address by Mousavi to the Iranian people:

In a Foreign Ministry statement read on Tehran radio today, Iran said that Israel should be annihilated and that implicit recognition of it by the Palestine Liberation Organisation ignored the inalienable rights of the Muslim Palestinan people.

The statement said that the only way to achieve Palestinian rights was continuation of all-out popular struggles against Israel.

In 1989, Mousavi called for Salman Rushdie to be killed. The Times (London) reported that "Mr Mir-Hossein Mousavi, the Prime Minister, said the Ayatollah Khomeini's order that Mr Rushdie should be killed 'will undoubtedly be carried out and the person who has become a tool of Zionists against Islam and brazenly attacked it and the Prophet will be punished', according to Tehran Radio." And in that same year, the Washington Post described Mousavi as a "leading hardliner," with links to regime attempts to assassinate political opponents in exile.

Read the whole thing. Ahmadenijad is unusually belligerent and unhinged even by Iranian standards, and so removing him can only be a good thing, but the reality is that the real power in Iran continues to lie with the very much unelected religious and security establishment; the mullahs control the selection of candidates and the scope of their authority, which is limited. A new front man won't change that. And the fact that Iranian "moderates" all end up saying about 95% of the same stuff as the "extremists" just illustrates the fact that the problems with the Iranian regime run far deeper than any one man.